A pump device for pressure-feeding liquid is disclosed in Japanese Patent Laid-Open No. 2009-156242 in which a pump case provided with a pump chamber in its inside is structured of a cover part and a bottom part which are superposed on each other in an upper and lower direction. In this pump device, an O-ring is disposed between the cover part and the bottom part and, when a screw is tightened for fixing the cover part and the bottom part, the O-ring is pressurized and thereby leakage of liquid from the pump chamber is prevented.
In such a pump device whose pump case is structured of two members, when the two members are superposed on each other to form a pump chamber, and when an O-ring disposed between two cases is damaged for example by turning the cover part in relation to the bottom part, the resulting effect is a reduction in preventing leakage of liquid from the pump chamber.